“Radiance Light Trends” Shows Changes in Earth’s Light Emissions

onMarch 6, 2019

Lighting trends at Tucson International Airport in Arizona, U.S., from 2012-2019. Data from “Radiance Light Trends”.

Many scientific datasets from satellites are in principle available for free, but that doesn’t mean that they are actually accessible to the wider public. A new web application aims to change that, at least for satellite imagery of Earth at night.

The app called “Radiance Light Trends” allows anyone with an Internet connection to quickly select a region or a site and analyze the trends in light emissions observed by satellites since 1992. The development of the webapp was guided by Dr. Christopher Kyba from the GFZ German Research Centre for Geosciences in Potsdam, Germany. It was produced as part of the GEOEssential project funded by the EU’s Horizon 2020 program, with the coding done by Jurij Stare of Deneb Geoinformation Solutions.

Satellites produce a great deal of data, so simply downloading the data can pose a challenge. “Before this app was developed, if someone new wanted to analyze trends in light emissions for a specific region, I expect it would take them at least a full day to do it,” said Kyba. “In addition to downloading the data, specialist knowledge of geographic information system software would be needed to select a region and analyze it.” With the “Radiance Light Trends” app, it is now possible for someone with no special training to produce a chart showing light trends in under a minute.

“Users can have the development of light pollution calculated for nearly any site or region in the world,” Kyba explained. “For example, take an area around Berlin, start the analysis and you will see how much brighter it has become in recent years.”

New satellite data is automatically entered into the database and taken into account for the calculation. This is particularly useful for interested citizens, environmentalists, or journalists, but also for municipal administrations and companies planning lighting measures. The app might also be useful for the analysis of natural hazards and the planning or the rebuilding of infrastructure.

Changes in lighting which can be tracked by “Radiance Light Trends” have a variety of causes, according to Kyba. One example he points to is Tucson International Airport in Arizona, where hundreds of outdoor lights were replaced in August to October of 2014, in order to reduce energy consumption and light pollution. A clear drop is visible for that location in “Radiance Light Trends”. Another example is light leakage from large greenhouses, which often introduces new light to areas that used to be quite dark. For instance, a large greenhouse about 350 kilometers south west of Moscow lights up the night with escaping light since 2015.

There are several options to choose from for displaying the satellite data in “Radiance Light Trends”. Users can add a color-coded projection onto a map of the Earth with annual or monthly data, or draw a shape around an area of interest to see a timeline of light data over several years on a monthly basis, for example. The data can also easily be exported in different data formats.

Kyba suggests that other satellite datasets could be made similarly accessible: “There’s no reason that a similar application couldn’t be produced for measurements of temperatures, or arctic sea ice, or any host of other environmental variables. With that in mind, we are planning on soon releasing the code underlying the web app under a license that will allow others to reuse it.”